In a small bowl, whisk cornstarch into one-fourth-cup whipped topping. Set aside.

In a medium saucepan, bring one-fourth-cup whipped topping, champagne, one-fourth-cup sugar and confectioners’ sugar to a boil over medium heat. Stir and turn down heat to simmer.

In a separate bowl, whisk egg and egg yolks together until pale yellow. Add cream and cornstarch mixture. Pour one-fourth-cup of the hot champagne and cream mixture into the egg and cream mixture. Whisk it constantly so the hot mixture does not cook the egg mixture.

Pour that mixture back into the saucepan. Whisk over medium-low heat until it thickens and coats the back of a spoon. As soon as it is thickened, remove from heat and whisk in margarine and vanilla extract.

Allow pastry cream to cool slightly and cover with plastic wrap pressed onto the surface of the custard so it doesn’t form a skin. Cool completely.

Place two cups sliced strawberries in a small bowl. Mash them coarsely with a spoon and add remaining one tablespoon sugar to release the strawberries’ juices.

In a glass trifle bowl, layer the bottom with about 10 hamantaschen cookies, starting with the perimeter and filling in the middle as you go. Place one and a half cups sliced strawberries on top, and half of the coarsely mashed strawberry mixture with its juices. Top with half of the champagne cream. Start a second layer and place another 10 cookies on top of the champagne cream. Then add another one and a half cups sliced strawberries, remaining mashed berries and juices, then cream. Beat remaining one cup whipping cream until soft peaks form. Top decoratively with whipped cream, remaining berries and crumbled hamantaschen.